PSI - Issue 57

7

Author name / Structural Integrity Procedia 00 (2019) 000 – 000

Kashif Kamran Toor et al. / Procedia Structural Integrity 57 (2024) 772–784

778

Fig. 6. (a) Global model cut boundaries; (b) Local FE model and load axis.

The INF are saved in matrix form and read into the global model to calculate the actual stress response by multiplying the environmental load effect at cut boundary sections. An example INF for the hot spot is given in Table 1.

Table 1. Example INF for the hot spot. Brace Stress DOF1 DOF2

DOF3

DOF4

DOF5

DOF6

Fatigue damages are then calculated for the stress response using joint specific design S-N curves. The parameters in Table 2 were applied for the selected hot spot.

Table 2. Fatigue parameters for the hot spot. Hotspot SN Curve

Plate Thk. [mm]

Ref. Thk.[mm]

Thk. Exp.

AT 1029

DNV-D

40

25

0.2

Then the fatigue damage was calculated using the hot spot stress and the relevant S-N curve. The total fatigue damage was then calculated based on Palmgren-Miner rule of linear summation. Note, for the type ‘b’ hot spot thickness correction is not required for the hot spot stress calculation according to DNV-RP-C203 (2016).

3. FE Model 3.1. General

A 3D mid surface model of the selected pile sleeve connection is created for FE analysis, see Fig. 3. The INFs were generated based on a linear static response with parameters in Table 3. The grouted connection was modelled as bonded contact. Based on sensitivity analyses it is indicated that this is a reasonable approximation. A local solid model at the weld notch was also analyzed serving as benchmark to evaluate the conventional stress extrapolation techniques. Sub modeling technique is used for the notch stress model. Finite element analyses were performed using the ANSYS software package. The finite element models were discretized using higher order shell elements, SHELL 281, for mid surface shell sections and a minimum element size of 4mm was used in the vicinity of the hot spot. For the notch stress model higher order solid elements, SOLID 186, was used for the local solid model. Linear elastic material properties were applied for all the models irrespective of modeling technique.

a

b